I'd advise staying away from a 606 entirely unless you want it from a collectors stand point, especially if its a gas /diesel. The diesel engine in them starts on gas, but runs on diesel, they have a carborator, distributor, injection pump, sparkplugs, injectors, and three sets of valves, starting, intake, and exhaust. Two fuel tanks... complete dual fuel systems. There was not too many of these tractors produced from new, most set up as western wheatlanders.
Because the head has so many holes in it, they are prone to warping and cracking, especially if they are not properly warmed up and cooled down after use. Compounding that, the starting valves and heads are getting rare, especially good ones. I've seen cracked heads sell for $2500, and repair is on the new owner, because they are that hard to find.
On that note, some had a straight diesel engine on them, that isnt too bad, just grumpy in the cold. Probably the best motor is the straight gas.
Another thing, the older torque amplifier style will let the tractor free wheel in low range. So your going down hill, and throw the t/a, and you just put it in neutral, and you can't pull the ta back in... hope your brakes are good... With the 66 series, they fixed that problem with the t/a's, those had lockup in low range on the t/a. There is conversion kits available to put the new t/a in a old tractor. To explain it a little better, any letter tractor - h,m,w,I, &o as well as the super and diesel's, any 350 thru 650, any 460 thru 660, any 506 thu 2806, any 656 thru 2856, with an original t/a has the old t/a.
Your ih's ending in 66,68,88,84, & 85 all have the new t/a in them. Part of the t/a test is to check that they hold back in low. Oh, 68's are collector specials too, they have v-8's instead of straight 6's
On the ih hydros, as long as they are maintained, as in oil level kept up, and temp kept down, maintence isn't that bad. They are just expensive to fix. Check with a case ih dealer in your area that was an international harvester dealer, they should be able to provide a diagnosis, or point you in the direction of someone who can. I'd sugest goign beyond just checking the filter for metal, I believe that they can use some gauges to check flow and pressure in those hydro units. As well there are some operational tests to perform.
As far a my tractor, Dad just said that its finally out running around, has a new shortblock c-200 installed, new oil pump, all new gaskets, freshly serviced and ready to go to work.
And the rototiller is waiting for it, as I have some foodplots to do with it, logs to skid, dirt to move, barn to clean and other loader chores....
